fix today memory after restart

internal/storage/history.go

@@ -2,6 +2,8 @@ package storage
 
 import (
 	"context"
+	"database/sql"
+	"errors"
 	"fmt"
 	"strings"
 	"time"
@@ -65,6 +67,21 @@ func (s *Storage) GetShowCounts(ctx context.Context, memoNames []string) (map[st
 	return result, rows.Err()
 }
 
+// GetLastShownToday returns the memo_name and tier of the most recently shown memo
+// within the given time range [from, to). Returns empty string if nothing was shown.
+func (s *Storage) GetLastShownToday(ctx context.Context, from, to int64) (memoName string, tier int, err error) {
+	err = s.db.QueryRowContext(ctx,
+		`SELECT memo_name, tier FROM show_history WHERE shown_at >= ? AND shown_at < ? ORDER BY shown_at DESC LIMIT 1`,
+		from, to).Scan(&memoName, &tier)
+	if err != nil {
+		if errors.Is(err, sql.ErrNoRows) {
+			return "", 0, nil
+		}
+		return "", 0, fmt.Errorf("get last shown today: %w", err)
+	}
+	return memoName, tier, nil
+}
+
 // RecordShow records that a memo was shown.
 func (s *Storage) RecordShow(ctx context.Context, memoName string, tier int) error {
 	_, err := s.db.ExecContext(ctx,